Recently, in accordance with an increase in an interest in an environment and energy in an automobile industry around the world, a study for improving fuel efficiency has been conducted, and research and development for weight reduction, miniaturization and function improvement have been continuously conducted in order to satisfy various needs of consumers.
In many cases, a hybrid vehicle adopts an idle stop and go (ISG) system automatically stopping an engine at the time of being stopped, for example, at the time of waiting for light to be changed, or the like, and restarting the engine by a manipulation of a transmission. However, even in the case of the hybrid vehicle, a cooling apparatus is operated by the engine. Therefore, in the case in which the engine is stopped, a compressor is also stopped, such that a temperature of an evaporator rises to deteriorate comfortableness of a user. In addition, since a refrigerant in the evaporator is easily vaporized even at room temperature, the refrigerant is vaporized for a short time in which the compressor is not operated, such that the vaporized refrigerant should be compressed and liquefied even though the engine is again operated, such that the compressor and the evaporator are operated. Therefore, it takes a long time for cold air to be supplied, to the interior, and an entire required energy amount is increased.
Here, the hybrid vehicle may further include a cold reserving evaporator to improve cooling performance and extend or delay an engine restart time.
As the related art, Japanese Patent Application Laid-Open Publication No. 2000-205777 (entitled “Cold Reserving Heat Exchanger”) has been suggested, which is illustrated in FIG. 1.
In a cold reserving heat exchanger 90 as illustrated in FIG. 1, a refrigerant path 91e through which a refrigerant flows and cold reserving material chambers 91f and 91f in which a cold reserving material is stored are formed integrally with each other by a tube 91 having a dual-pipe structure, and a path 94 of a fluid heat-exchanged with the refrigerant is formed outside the tube 91 having the dual-pipe structure.
However, in the cold reserving heat exchanger as illustrated in FIG. 1, the tube is formed by bonding several plates to each other, such that an occurrence frequency of a bonding defect is high, the tube is formed in the dual pipe structure, such that it is difficult to manufacture the tube, and in the case in which the bonding defect occurs, the refrigerant and the cold reserving material may be mixed with each other. In addition, even though the bonding defect occurs, it is difficult to find a portion in which the bonding defect occurs.
In order to solve the problem as described above, a cold reserving heat exchanger including a plurality of tubes disposed in three rows in a width direction and including a first-row tube and a third-row tube in which a cooling fluid is circulated and a second-row tube in which a cold reserving material is stored; and an upper header tank and a lower header tank fixed to both ends of the tubes in a length direction, including a first space portion that is in communication with the first-row tube, a second space portion that is in communication with the second-row tube, and a third space portion that is in communication with the third-row tube, which correspond to three spaces separated in the width direction, and having a header and a tank coupled to each other, as illustrated in FIG. 2A, has been developed.
The cold reserving heat exchanger requires an additional structure in order to move a refrigerant between a first row and a third row, and in an exemplary embodiment of FIGS. 2A and 2B, a refrigerant moving path portion 13 for moving the refrigerant between the first row and the third row is further included at one end portion of a lower tank 12.
In this case, in the cold reserving heat exchanger, partition walls partitioning the fluid, between first to third rows occupy the respective volumes, such that a width of an evaporator is increased, and a length of the cold reserving heat exchanger is increased due to the refrigerant moving path port ion.
In addition, a mounted space of the cold reserving heat exchanger is limited, and particularly, spaces of the upper header tank and the lower header tank are also limited. In the case of prioritizing heat radiation performance as compared with cold reserving performance in the cold reserving heat exchanger, spaces of the first space portion and the third space portion should be increased in order to improve the heat radiation performance, and in the case of prioritizing the cold reserving performance, a size of the second space portion in which cold air may be stored should be increased. Therefore, there is a limitation in uniformly increasing ail the spaces.
In addition, it is difficult to optimize a design so as to improve both of the heat radiation performance and the cold reserving performance.
Further, referring to cross sections of tubes of FIG. 2B illustrating a cross section taken along line A-A′ of FIG. 2A, in the cold reserving heat exchanger, all of the tubes of the first to third rows have the same shape. It is difficult to change shapes and structures of the tubes, for example, to increase cross-sectional areas of the tubes of the first to third rows in order to improve the heat radiation performance in the case of prioritizing the heat radiation performance of the cold reserving heat exchanger as compared with the cold reserving performance or in order to increase a size of the tube of the second row in the case of prioritizing the cold reserving performance.
Therefore, it is necessary to develop a cold reserving heat exchanger of which an increase in a volume is minimized in a more compact structure.
In addition, it is necessary to develop a cold reserving heat exchanger of which both of heat radiation performance and cold reserving performance may be improved by optimizing areas of first to third space portions in a header tank of the cold reserving heat exchanger.
Further, it is necessary to develop a cold reserving heat exchanger of which both of heat radiation performance and cold reserving performance may be improved by changing shapes and structures of tubes of first to third rows of the cold reserving heat exchanger.